Typically, when someone presents a demonstration of “Doom running on X,” it’s a way to demonstrate how powerful low-end computing has become. The reason we use Doom for this purpose, I suspect, is because Doom is more-or-less the father of the FPS genre. This tendency also results in Doom being played on devices that aren’t a lot of fun to play with (which is integral to this story). This story is a bit different. The device in question — a Ti-84 graphing calculator — is long-conquered territory, as far as Doom is concerned. What sets this project apart is the fact that the graphing calculator is powered entirely by potatoes.
Ever heard of a potato battery? Stick zinc and copper electrodes into a potato, and voila — you’ve got yourself a tiny, crappy battery. Boiling the potatoes first helps. The electrical output from this kind of battery is tiny — Wikipedia helpfully notes that “We can conclude that it would take more than 6 million lemons to give us the power of an average 4320W car battery.” This is not a task for the faint of heart or those with less-than-strong stomachs.
Intrepid Youtuber Equalo had a dream: To build a potato-powered Raspberry Pi and play Doom on it. This was going to be difficult from the start — potatoes can be used as batteries, yes, but they’re bad at it — and even a Raspberry Pi Zero (the type used) requires 120-140 milliamps to boot with HDMI disabled. Keeping HDMI enabled would have cost additional power.
This initial attempt fizzles out after the 100 pounds of potatoes Equalo boiled and cut into ~7 pieces fail to generate the appropriate amount of power. The spuds top out at around 80mA and 4.5V. It’s not enough juice, and while his monitor recognizes when an HDMI plug has been connected, nothing else happens. Based on the results he got and the fact that he started with 100 lbs of potatoes, it looks to me like he might have needed another 50 to 100 lbs to actually achieve his goal. That’s a lot of potatoes.
But Equalo, spud-stud that he is, has another trick up his sleeve. Instead of attempting to power a Raspberry Pi, he decides to go for a Ti-84. Ti-84s only use 10-30 milliamps, which makes sense, considering the Zilog Z-80 that powers it only runs at 15MHz. To put this in perspective, the Z-80 was first developed during the Carter Administration and current eZ80 versions of the chip clock up to 50MHz. The Ti-84 Plus is basement-level equipment even by the standards of minimally-powered embedded devices, and if Texas Instruments had been willing to allow end-users to have more than 24KB of RAM to play with, the version of Doom he eventually gets running wouldn’t look like a Vectrex game.
The brand-new, yam-energized Tater-84 Plus proves capable of zipping through the game, making this the first time to my knowledge that any computing device capable of playing Doom has been powered entirely by potato. The experience on a Z80 with 24KB of RAM is far from what you’d want, but it is Doom (at least the Ti-84 Plus version), and it is being powered by a massive, rotting organic battery.
Oh yeah. We didn’t mention that part. During the six days it took the ‘Tuber to boil, cut, wire, and construct his battery, the potatoes — having no idea they were being used in such an illustrious project — began the rote process of decomposing. By day 6, you can hear Equalo struggling for air that doesn’t smell like the world’s worst storage cellar.
His final verdict is that you should, under no circumstances, attempt this project. The potatoes are expensive, the power they yield is tiny, and they rot within days. But as far as unusual feats go? He’s got that on lock. Also, just in case you were curious, apparently a garage full of rotting potatoes smells a lot like rotting fish.
Special to Equalo’s wife, who helped wire the battery together and apparently put up with the month-long project in good humor.